Well, I'm not a professional space fantasy writer, but it seems to me they could have had Thawn conquer several planet's worth of spacefaring societies during the last in-universe decade, and united them under his rule. When Baylan/Morgan/Sabine got to this new galaxy, they could have been intercepted by a band of scrappy outlaws, who would be turn out to be former top commanders of these societies. Their peoples had always been consumed by petty rivalries, but once Thrawn arrived, they belatedly banded together against him - to no avail. And now this ragtag crew is so desperate for an advantage, and so determined to keep Thrawn contained, that they're risking everything in order to intercept any new arrivals to their corner of the cosmos.
This group would take Baylan and Co. prisoner, and start to befriend Sabine, as she was
their prisoner. Sabine would get to like them, and they'd discuss ways to imprison her captors, and send her home. Sabine would insist she'd have to find Ezra first, and their commander would be sympathetic, but say that her staying would be too dangerous. Or, heck, maybe Ezra would be a
part of this crew himself. Sabine could urge him to return home, but Ezra could point out that, with the Empire defeated, his skills are needed more here.
Then,
bam, out of nowhere, Thrawn's forces show up. The outlaws prepare to fight, but...
sabotage! It turns out Thrawn figured out a way to covertly communicate with their navigator, and used his psychological tricks to flip him. The group is forced to surrender without a shot, and while Thrawn keeps his word to spare the navigator and other personnel, he has the group's leaders summarily executed for treason against himself. In a blind rage, Ezra rushes at Thrawn... and Baylan throws a knife through his back and into his heart. Thrawn smiles at Baylan, and, as Ezra gasps his last, suggests this could be the beginning of an intriguing partnership. Roll credits!
Now,
that could have been an
episode.
That could have been a proper introduction for a
Big Bad.